1. Field of the Invention
This invention relates to a radio telephone device consisting of a base unit connected to wire circuits such as subscribers' lines and a radio telephone connected to the base unit via a radio circuit, and more particularly to a radio telephone device which is capable of dialing udner on-hook state from the radio telephone.
2. Description of the Related Art
The following is an example of a radio telephone device consisting of a base unit connected to wire circuits and a radio telephone connected to the base unit via a radio circuit. FIG. 7 illustrates the configuration thereof, which consists of a base unit 2 connected to a subscriber's line 1 and a radio telephone 4 connected to the base unit 2 via a radio circuit 3.
The base unit 2 includes a transmitter (TX) 22 for which a transmitting and receiving channel is allocated by a synthesizer (SYN) 21 and a receiver (RX) 23, modulates talking signals arrived from the terminal of a correspondent for conversation via the subscriber's line 1 during conversation by said transmitter 22 after passing through a line relay 24 and a hybrid circuit 25 to sent out to the radio circuit 3 from a transmitting antenna 26. At the same time, the base unit 2 demodulates radio talking signals arrived from the radio telephone 4 via the radio circuit 3 by the receiver 23 via a receiving antenna 27, and then sends out to the subscriber's line 1 via said hybrid circuit 25 and line relay 24. The base unit 2 also includes, as circuits necessary for the connection between the subscriber's line 1 and the radio telephone 4, a signal reception-detection circuit 28 for detecting 16 Hz calling signals arriving from a switchboard, a received electric field-detection circuit (C-DET) 29, an identifying signal-detection circuit (ID-DET) 30 and a control circuit (CONT) 31. The received electric field-detection circuit 29 consists of a carrier squelch circuit or a noise squelch circuit, which monitors the arrival of radio waves from the radio telephone 4. The identifying signal-detection circuit 30 collates an identifying signal (ID code) which as been predetermined by a combination of the base unit 2 and the radio telephone 4, and notifies the result of the collation to the control circuit 31. The control circuit 31 includes, for example, a microcomputer as a main control unit, and performs various connection controls. A rectified stabilizing circuit 32 supplies a predetermined operating voltage Vcc from the commercial power supply output to each circuit in the base unit 2, and at the same time supplies the same as a charging voltage to the radio telephone 4 via a feeding terminal 33.
On the other hand, the radio telephone 4 includes a transmitter (TX) 42 for which a transmitting and receiving channel is allocated by a synthesizer (SYN) 41 and a receiver (RX) 43 like said base unit 2, receives and demodulates radio talking signals arrived via the radio circuit 3 during conversation by the receiver 43 via a receiving antenna 44 to subsequently output as sounds from the receiver 45, and at the same time demodulates talking signals input from a transmitter 46 by the transmitter 42, and subsequently sends out to the radio circuit 3 via a transmitting antenna 47.
A display unit 57 which uses a liquid crystal display and the like for the element thereof is for displaying the dial number and the like of a subscriber in correspondence input by a dial key 49.
This radio telephone 4 also includes, as circuits necessary for the connection between said base unit 2 and a switchboard, a dialing switch 48, a dial key 49, a received electric field-detection circuit (C-DET) 50, an identifying signal-detection circuit (ID-DET) 51, A control circuit (CONT) 52 which performs various connection controls with a microcomputer as a main control unit, and a sounder 53 which generates ringing. A battery 54 is charged by the operating voltage Vcc fed from said base unit 2 via a charging terminal 55.
Under such a configuration, when signal reception occurs, the base unit 2 detects the occurrence of the signal reception by the signal reception-detection circuit 28, indicates an unoccupied transmitting and receiving channel to the synthesizer 21 by the control circuit 31 to operate the transmitter 22 and the receiver 23, respectively, and sends out an ID code and a reception signal to the radio telephone 4.
Meanwhile, the radio telephone 4 is performing intermittent receiving operation during standby by the receiver 43, and when radio waves arrive from the base unit 2 under this state, the radio telephone 4 detects the same with the received electric field-detection circuit 50, and at the same time colates the ID code sent from the base unit 2 by the identifying signal-detection circuit 51. When the radio telephone 4 judges after the result of the collation that the signal reception is to the own device, it indicates the transmitting and receiving channel to the synthesizer 41 by the control circuit 52 to make the transmitter 42 and the receiver 43 in continuous operation state, and subsequently retransmits the signal reception response signals to the base unit 2, and at the same time generates a ringback tone signal from the sounder 53 to notice the occurrence of signal reception to the subscriber. When the subscriber responds to this call by turning on the dialing switch 48, the fact is sent out from the transmitter 42 of the radio telephone 4 to the base unit 2, and as a result the base unit 2 turns on the line relay 24. Consequently, the radio telephone 4 is connected to the caller, and hereafter conversation becomes possible between the both parties.
When the subscriber turns on the dialing switch 48 of the radio telephone 4 under standby state, the radio telephone 4 indicates a specified transmitting and receiving channel to the synthesizer 41 by the control circuit 52 to thereby continuously operate the transmitter 42 and the receiver 43, respectively, and at the same time sends out an ID code and a dialing signal. When radio waves have arrived from the radio telephone 4, the base unit 2 detects the same with the received electric field-detection circuit 29, and at the same time collates the ID code by the identifying signal-detection circuit 30. When the base unit 2 recognizes that there is a connection request to the own device after the result of the collation and at the same time confirms the arrival of the dialing signal, it produces a dialing response signal by the control circuit 31 to transmit the signal along with the information on the indication of the transmitting and receiving channel from the transmitter 22 to the radio telephone 4, and thereby makes the radio telephone 4 set the transmitting and receiving channel for conversation. After this control operation, the line relay 24 is turned on to make the d.c. loop of the subscriber's line 1. Further, when the subscriber inputs under this state the telephone number of the correspondent by the dial key 49, the radio telephone 4 sends out that key code data from the transmitter 42 via the radio circuit 3 to the base unit 2.
At this moment the telephone number of the correspondent which has been key input is displayed on the display unit 57, and it is possible to confirm if the telephone number input is correct.
The control circuit 31 of the base unit 2 performs switching control of the line relay 24 in accordance with said key code data to send out dial pulses to the subscriber's line 1. Consequently, calling to the desired correspondent for conversation is performed, and when the called side responds thereto, the connection between the radio telephone 4 and the called side is made thereafter and conversation becomes possible.
That is, by using such a device, it is possible to perform conversation completely in the same way as the case using a normal wire telephone directly connected to the subscriber's line 1.
Now, it has recently been considered to give to this kind of device the so-called on-hook dialing function which can perform calling operation even without approaching the transceiver of the radio telephone 4 to the subscriber's face. In order to perform on-hook dialing, however, it is necessary to prepare a loudspeaker of relatively large size (about 5 cm in diameter) which outputs loudly signals or sounds on the subscriber's line and a driving circuit thereof. On the other hand, the radio telephone 4 is desired to be of small size and light weight in order to be easily portable, and at the same time the consumption current thereof is required to be as small as possible because a battery is used as the power supply thereof. Hence, it has been extremely difficult to give said on-hook dialing function to a radio telephone device.
As described above, the conventional device has disadvantages that it is difficult to be provided with on-hook dialing function, and in the case of providing that function a larger size of the radio telephone and a shorter life of the battery are inevitable. The present invention, in paying attention to this point, intends to provide a radio telephone device which can realize on-hook dialing without causing a larger size of the radio telephone and a shorter life of the battery.